86 



papillae about four on each side, very small, somewhat irregular. 

 Madreporic shield lying at the corner of the interbraehial space ; 

 broader than long, plainly made up of irregular, short, thickened 

 tubes, soldered side by side. The space occupied by the tentacle 

 pores and the covered under arm-plates is sunken, forming a shallow 

 trench, the joints being indicated by obscure cross hues. Beyond the 

 disc, the joints are marked by depressions between them; their outer 

 and inner ends are thickened on the sides, making a series of very 

 distinct double ridges along the sides of the arm. The under side of 

 the arm, within and near the disc, is covered by a close pavement of 

 flattened grains ; it is very distinct from the sides and upper surface, 

 which are beset with fine, rounded grains, and are separated from the 

 lower surface by a sunken hne. Along the upper surface of the arm 

 runs a distinct median furrow. Radial ribs running cpiite to the 

 centre of the disc, prominent, their outer ends cut abruptly off, mak- 

 ing a concave scar, length to breadth, 17:4; they are closely beset 

 with microscopic, thorny stumps or grains, some of which end in 

 three or four distinct thorns. The same thorny grains are found, but 

 smaller and more scattered, on the interbraehial spaces below ; and 

 a few also on the depressed parts of the upper surface of the disc. 

 At the tips of the arms and on the smaller twigs there are, as usual, 

 double vertical rows of grains, bearing hooks. Tentacle-scales, one 

 or two, small and difFicult to see, extending inward as far only as the 

 fourth fork of the arm. Color, in alcohol, above, dark purplish- 

 brown, varied with black; below, interbraehial spaces the same; 

 under surface of arms much lighter. Zanzibar. 



Notes on the Cretaceous and Carboniferous Eocks of 

 Texas. By Jules Marco u. 



A short time after my last return to Boston, June, 1860, I received 

 two memoirs by Dr. B. F. Shumard, On the Geolorjy of Texas, in 

 which that eminent paleontologist has expressed opinions differing 

 from those published by me several times from the year 1854 to 1859. 

 From the nature of Dr. Shumard's memoirs, wliich contain only short 

 notices, without descriptions or figures of the contested species of 

 fossils, without geological maps, and without real sections of the rocks 

 identified, I did not intend to give my views on the subject, especially 

 after having repeatedly explained the stratigraphical relations of the 

 rocks west of the Mississippi. 



In the mean time I wrote a letter, in September, to Dr. Shumard, 

 telling him that although his memoir On the Cretaceous Strata of Texas 

 was very interesting, I could not agi-ee with him as to the succession 

 given by him in his theoretical section, but tliat I hoped one day we 

 might meet, ])erhaps at Fort Washita, or even at Pyramid jNIount, 

 and then settle amicably together our diiferent views. Dr. Shumard 



